Hmm, interesting proposition. Instead of fixating on heart rate zones, monitoring fatigue levels could indeed provide valuable insights. However, it's not a matter of simply swapping one metric for another. Fatigue is multifaceted, influenced by many factors both internal and external.
While muscle tension and bike vibrations offer intriguing data points, let's not forget the role of sleep quality, nutrition, and mental stress in fatigue development. Overlooking these could render any new metric ineffective.
And then there's the question of how to interpret this data. Fatigue isn't binary; it's a spectrum. How do we set actionable thresholds? Could this lead to another layer of obsession, replacing one set of numbers with another?
In the end, perhaps the key isn't in the metrics themselves, but in how we use them. A balanced approach, incorporating various data points and human factors, might be the most effective way to optimize efficiency and prevent burnout. What do you think, fellow cyclists? :kissing\_heart: